Human Embryonic Stem Cells Stem

Human Embryonic Stem Cells

Stem cell studies are on the very cutting edge of biological advancement and research. These undifferentiated cells have the potential to become any cell in the body, from a simple part of a hair follicle to a complex neuron. Because research into this area is so new, there are still many scientific and ethical dilemmas surrounding stem cell research, especially research that involves human embryonic stem cells. These are the cells that have caused so much media and political attention over the past decade; the moral and ethical debates surrounding their uses are often heated and always too complex and controversial to allow for the emergence of a clear conclusion.

The issue comes from the fact that embryos are often destroyed in the creation and extraction of human embryonic stem cells, and though embryos are not typically created for this express purpose, many individuals, groups and politicians still find the practice morally repugnant. Fro this reason and other ethical considerations, funding has been less available for human embryonic stem cell research, which has slowed the advancement of this emerging and immensely applicable branch of biological and medical science.

While the ethical considerations of human embryonic stem cell research may call research methods into question, the growth in scientific knowledge and advances in medical treatment that have been derived from such research is anything but questionable. Human embryonic stem cell research has led to a vastly increased knowledge of genetic manipulation, and many therapies and treatments have already been derived from stem cell introduction and manipulation (Fenno et al., 2008; Garg, 2008; Mao et al., 2009; Nury et al., 2009). Continuing research promises to provide even more questions, answers, and treatments to further expand our understanding of genetics and the benefits -- and dangers -- involved in genetic manipulation.

Of course, the ethical and scientific aspects of the research cannot and should not be completely divorced from each other; another factor affecting current human embryonic stem cell research is the fact that most peer reviewed journals have voluntarily withdrawn from publishing the results of any attempts at therapeutic cloning (Meyer, 2008). Therapeutic cloning is just one of the ways -- one of the more controversial ways, certainly -- that human embryonic stem cells have been used in scientific and medical advancement. In this process, embryos are cloned using genetic processes developed over the past two decades in an attempt to more carefully match the recipients of stem cell therapies with cells that they are compatible with in immunologic terms (Meyer, 2008). This belies some of the pitfalls with stem cells; though often touted in the media as genetic fixes for many diseases, the realities are much more complex.

Stem cells are pluripotent undifferentiated cells that exist in various places even of the adult body throughout life. All cells in an organic body, ignoring any possible mutations that actually occur somewhat regularly with insignificant or completely null effects, contain the genetic blueprint for the entire organism. That is, the strand of DNA that is found in a human skin cell, or intestinal cell, or liver cell, contains the genetic information that encodes for hair color, skeletal growth, biological gender, and everything else that genetically defines us as individuals. Almost all of the cells in the body, however, are differentiated -- they express only a very limited part of the genetic information contained in their nuclei, allowing them to function as a skin cell or intestinal cell or liver cell. They would not be of much use otherwise. Stem cells, however, are undifferentiated, and have the potential to express any piece of DNA.

At first, stem cells were only accessible, identifiable, and able to be isolated in embryos, and though other methods for retrieval and even the replication of stem cells are being developed, some of them with great success, embryonic stem cells remain the most efficient and viable form of stem cell treatment (Meyer, 2008). This raises ethical questions that seem to argue for the continuation and progression of human embryonic stem cell research and treatments, as the methods and practices derived from such research can be used to save many lives and improve the quality of life for countless numbers of people much sooner, more safely, and more cheaply -- which means the treatments will be available to a far wider range of people -- than other therapies, including other non-embryonic stem cell therapies (Meyer, 2008).

Indeed, setting aside the problems of stem cell identification and retrieval from adult organisms -- including humans -- the efficacy of all stem cells is not equal. Current evidence suggests that human embryonic stem cells are "possess exceptional self-renewal and pluripotency properties" when compared with stem cells of other classes (Garg, 2008). Much of this increased pluripotency is believed to be in some way derived from or related to the embryonic stem cell's ability to become a part of any of the three germ layers that make up a more advanced human embryo (Garg, 2008). These layers rapidly and radically differentiate, and stem cells retrieved before this stage are simply more physiologically malleable than any others. The processes and factors that make this possible are still not fully understood, but ethical concerns may render the point moot.

Most currently practicable stem cell therapies involve tissue repair and regeneration, which makes sense given the simple function and ability of the stem cell to become almost any specific type of cell (Garg, 2008). But although human embryonic stem cells are the most capable type of stem cell in this regard, political, religious, and ethical barriers to research have caused human embryonic stem cell research to flounder in recent years, and alternative therapies are now being more actively pursued by many researchers and laboratories (Garg, 2008). Different types of stem cells have been shown to be more effective than others in certain situations, and the number of ways in which to drive and apply stem cells continues to increase.

Most opportunities for stem cell retrieval still depend on an embryo, though in utero situations actually provide more opportunities for collecting pluripotent stem cells than artificially created or lab-cloned embryos (Garg, 2008). Evidence suggests that these cells, though present in such places as the amniotic sac and the placenta, which are mostly biological products of the mother's body, the stem cells found in these places are almost certainly products of the growing embryo and fetus (Barcena et al., 2009). Again, the mechanisms and factors that contribute to subtle changes in these stem cells are not full understood, but the fact that even stem cells retrieved from non-embryonic locales still bear the stamp of their embryonic stem cell origins is another strong indicator that embryonic stem cells represent the highest pluripotency.

This does not mean that other stem cells are not effective, however, but merely that they are less effective and less widely usable than human embryonic stem cells. Certain types of stem cells still show significant signs of pluripotency; endometrial stem cells found in menstrual blood have even shown the ability to differentiate into neural cells as well as many others (Garg, 2008).

With current research, some of the mechanisms that determine the differentiation of human embryonic stem cells are being better understood, which could aid in the development of future therapies using both human embryonic stem cells and less controversial stem cells from other sources. Miguel Barthelery, Amritha Jaishankar, Ugur Salli, and Kent E. Vrana conducted research using human embryonic stem cells in relation to nerve differentiation (Barthelery et al., 2009). In the research phase of their study, they noticed that a certain protein known as Reptin52 was present in much higher qualities in the non-adhering colonies of nerve cells known as neurospheres, which formed the basis of the nervous system in developing embryos (Barthelery et al., 2009). They also found that this protein was more prevalent in human embryonic stem cells in the process of becoming neural cells, which of course is what the cells in the neurospheres -- like all human cells -- had all started out as (Barthelery et al., 2009).

The research team then began experimenting with in vitro manipulation of human embryonic stem cells and there response to Reptin52 as well as other chemicals (Barthelery et al., 2009). The process of genetic transcription is a very delicate one, and mistakes are made in cells constantly. The alteration of protein levels or other chemical balances can have a huge effect on normal cell division, but the effects are far more profound in the differentiation of pluripotent human embryonic stem cells. Though not solely responsible for the differentiation process, Reptin52 is believed by the researchers to be one of the primary causes of human embryonic stem cell differentiation into neural cells, in addition to the already established belief that the same protein plays an important role in transcription overall (Barthelery et al., 2009).

This study does a great deal in advancing the knowledge of the differentiation of human embryonic stem cells, specifically in regards to their differentiation into neural cells. It is only a drop in the bucket of the currently available knowledge on neural differentiation, however. According to Human Embryonic Stem Cells: A Practical Handbook, there are seventeen acknowledge and reviewed methodologies for differentiating human embryonic stem cells into neural cells (Walsh, 2008). The incompleteness and erros of this same book, however, reflect the dearth of research into the area of human embryonic stem cell research (Walsh, 2008). Though many advances have been made -- and indeed are being made right now -- the ethical concerns regarding human embryonic stem cells have proven a greater obstacle than the scientific community can fully surmount. This is not to say that ethical considerations are the only reason for a lack of knowledge, either; science, when performed carefully, is usually a slow process, and the benefits and implications of human embryonic stem cell research are far too meaningful and profound to warrant any rushing to hasty conclusions.

It is true that research has provided many insights into specific types of differentiation. The understanding of the differentiation process as a while, however, is still very much in need of further research before a full and accurate description of the processes and mechanisms involved can be achieved. The amount of time that genetic processes themselves have begun to be understood on a physiological and chemical level can only be measured in decades; research into the basic transcription process is not complete. The more complex process of differentiation in human baryonic stem cells is still many years away from a full understanding.

Research presses on, however, and the differentiation of human embryonic stem cells into cardiac and myocardial tissue is another particular area of research that has been receiving much attention lately. The heart is the first organ to be formed in the embryo, and this process occurs within the first few days of conception (Nury et al., 2009). The embryonic stem cells that make up the heart and the constituent vessels must differentiate very early, then, and for this reason they have long fascinated the scientific and medical community (Nury et al., 2009). In a literature and methodology review, David Nury, Tui Neri, and Michel Puceat describe the various methodologies that have been observed and experimentally replicated -- or entirely created through innovative thinking and technologies -- for differentiating human embryonic stem cells in heart tissue and related components (Nury et al., 2009).